It can be seen in the results, as De La Rosa held the Anaheim Angels to just one run in seven-plus innings of work on Sunday, striking out eight in the Boston Red Sox's 3-1 win. It can be seen in his slider -- he throws two of them now, one slower than the other, to keep hitters guessing. And it can be seen in his fastball velocity.

He doesn't need to throw 100 mph to get batters out.

De La Rosa averaged just 93 mph on his fastball Sunday, the lowest average speed he's posted in a major league start, according to BrooksBaseball.net. While he was averaging 97 mph on his fastball earlier this year, his velocity has been on a steady decline, though his performance has gone a different direction.

"He was able to add and subtract to his fastball," manager John Farrell said after Sunday's start. "He always has that changeup to which to go to, but just the overall relaxation and confidence is really showing through."

De La Rosa, throwing to rookie catcher Dan Butler, was in command from start to finish, allowing just five hits.

"I feel confident right now," he said. "I feel like everything is working."

He can still dial it up. De La Rosa hit 98 mph on the radar gun at least once, so he's not throwing meatballs. He's just picking his spots.

When Johan Santana transitioned from a reliever to a full-time starter in 2004, the first year he won a Cy Young Award, it was said he purposely threw with less force. The idea was to save the heat when he needed it rather than emptying the tank early in games. Justin Verlander has made a name for doing just that.

With a 2.25 ERA over his last three starts and 3.21 ERA on the season, De La Rosa has been the most impressive young starter the Red Sox have tried out this season. While Allen Webster and Brandon Workman have been hit-or-miss, De La Rosa has allowed three runs or less in eight of his 11 starts.

"I think overall, it's been more his ability to consistently command a baseball in the bottom of the strike zone," Farrell said. "When he's gotten into some fastball counts he's gone to the slider on occasion. To me it's been more just overall fastball location that's been the difference."

Location, not speed.

"I think his fastball command was what the key was," Butler said. "He was able to throw his fastball early in the count to get guys swinging and teach them the fastball. After that, he was able to keep them off balance with the offspeed. He was able to get them on the fastball first."

Now two years removed from Tommy John surgery, the 25-year-old is growing into a pitcher the Red Sox believe can be a top-of-the-rotation starter.

"I just think this year is completely different than what we saw last year, his first year in the organization," after he was traded from the Los Angeles Dodgers, Farrell said. "It was a rehab year for him. This has been one in which he's going out to pitch and compete and show his feel and touch inside a given game and that was the case again today."